[llvm] [VPlan] Introduce ExitPhi VPInstruction, use to create phi for FOR. (PR #94760)

[via llvm-commits]

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@@ -1191,6 +1200,10 @@ class VPInstruction : public VPRecipeWithIRFlags {
     SLPStore,
     ActiveLaneMask,
     ExplicitVectorLength,
+    /// Creates a scalar phi in a leaf VPBB with a single predecessor in VPlan.
+    /// The first operand is the incoming value from the predecessor in VPlan,
+    /// the second operand is the incoming value for all other predecessors.
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ayalz wrote:

Worth adding that other predecessors are **currently** outside VPlan's scope.

https://github.com/llvm/llvm-project/pull/94760